This invention relates to a digital x-ray imaging method and system for producing soft tissue images and bone/calcification images for radiography and mammography and, more particularly, to such a digital x-ray system employing dual (i.e., two different) x-ray energies, obtained by rapidly switching an x-ray energy source between low and high energy levels, and using a single large area pixelated digital x-ray detector to capture the resulting and respective, dual energy x-ray images. The dual energy images are processed, with a pre-calibrated database and adjustable parameters, to produce respective, and separate, soft tissue images and bone/calcification images, affording enhanced visibility of any nodules or clusters of calcification, facilitating earlier detection of lung and/or breast cancers.
In xe2x80x9cnormalxe2x80x9d projection x-ray radiographic and mammographic images, nodules or clusters of calcifications can be obscured by structured noise/background, i.e., signal noise in the detected x-ray image caused by irradiation of bone structure (e.g., ribs or spine) or by contrast effects from, e.g., glandular and fatty tissues. In an effort to reduce such noise/background, dual energy x-ray imaging has been explored extensively, with both film/cassette systems and also digital systems.
Most of the early work in this field was based on film/cassette systems and, of necessity, employed a single x-ray energy spectrum and dual detectors. Particularly, with film/cassette systems, rapidly switching between high and low levels of x-ray energy (kVP) and using a single film/cassette for each image is not technologically feasible. Further, the limited dynamic range and lower detective quantum efficiency (DQE) of film/cassette systems preclude any such dual energy applications. The images obtained, moreover, were not acceptable.
Digital systems employing dual energy x-ray imaging offered at least the potential of improved images; however, there is a need in such systems of an increased separation of high and low X-ray energy levels yielding a practical, effective and efficient system performing dual energy X-ray imaging.
The present invention utilizes a dual energy x-ray digital imaging system that includes an x-ray generator capable of switching from high energy to low energy rapidly (e.g., on the order of ms), a single, pixelated digital x-ray detector, a computer, a display unit and related software to acquire and process the high and low energy x-ray images for display.